This invention relates to the production of patterns on a substrate having regions with different compositions or different surface treatment. More particularly, it relates to a method of producing fine patterns on substrates used in, for example, the microelectronics industry on which electronic devices are fabricated. It is also related to devices fabricated in accordance with the methods. The patterns are fabricated accurately and inexpensively without the use of lithography. The present invention also provides many additional advantages, which shall become apparent as described below.
A number of applications and technologies involve structures having a well-defined arrangement of chemically distinct components at the surface of a substrate. A common example is a substrate surface having metal conductor regions separated by insulator regions. Normally, these structures are defined by patterning processes such as lithography, embossing, and stamping, and have length scales ranging from 10nanometers to several microns. In many of these systems it may be necessary or highly beneficial to apply an additional component or treatment to only one of the components at the surface. One technique for performing this task is through the use of a mask to protect regions where this additional application or treatment is not desired. Effectively, the mask material directs this treatment to the intended surfaces that are fully exposed. Unfortunately, typical procedures to generate a mask by lithographic or other means can be expensive and error prone. Thus, a method in which these conventional approaches can be circumvented would be highly advantageous.
A particular example in which such strategies would be useful involves integrated circuits comprised of metal and dielectric components. It is widely known that the speed of propagation of interconnect signals is one of the most important factors controlling overall circuit speed as feature sizes are reduced and the number of devices per unit area is increased. Throughout the semiconductor industry, there has been a strong drive to reduce the dielectric constant, k, of the dielectric materials existing between metal lines and/or to minimize the thickness of layers having comparatively larger dielectric constants, e.g., cap barrier layers. Both of these approaches reduce the effective dielectric constant, keff, of the components between metal lines, and as a result, interconnect signals travel faster through conductors due to a reduction in resistance-capacitance (RC) delays. Unfortunately, these strategies are difficult to implement due to limitations in maintaining significant properties, i.e., mechanical, barrier, electrical, etc., that result with a reduction in thickness or change in the chemistry of the layers.
This invention relates to a method to fabricate mask layers onto a pre-patterned substrate having two or more chemically distinct surface regions. The mask layer is deposited by a selective reaction approach that provides self-alignment of the layers. This method can apply to any technology or application involving a chemically or physically heterogeneous substrate including: interconnect structures for high speed microprocessors, application specific integrated circuits (ASICs), flexible organic semiconductor chips, and memory storage. Other structures that can be fabricated utilizing this method include: displays, circuit boards, chip carriers, microelectromechanical systems (MEMS), chips for hi-thoughput screening, microfabricated fluidic devices, etc. The utility of this method stems from a simple and robust means in which the replication of a patterned substrate to generate a mask layer can be performed, circumventing the requirement for expensive and error prone methods, such as lithography. Thus, the present invention provides an extremely advantageous alternative to the prior art techniques.
In the example of integrated circuits, the effective dielectric constant is reduced by the use of a process wherein layers are selectively placed upon the metal lines. To do this, mask layers are first applied to the dielectric or hard mask surfaces. In accordance with the invention, these layers are generated by mechanisms involving selective chemical reactions as described below. The layers can be self-aligned such that lithographic processes are not required to define the features. Upon self-alignment on the dielectric/hardmask surfaces, these layers, can then be used as a mask for subsequent deposition of other layers which serve as diffusion barriers to copper, oxygen and/or water, layers which reduce the electromigration attributes of the metal lines, and seed layers.
Thus, in the example of integrated circuits, the use of the self-aligned masks allows a simplified fabrication process in which the effective dielectric constant between metal lines can be reduced through selective application of various materials to the metal lines. This is central to maximizing the propagation speed of interconnect signals and ultimately provides faster overall circuit performance. Furthermore, this invention leads to a higher level of protection and reliability of interconnect structures as the errors attributed to conventional patterning methods are eliminated and to reduced processing costs. Although the utilization of the self-aligned masks is described for integrated circuits, this method is useful for any application wherein the modification of a specific component in a pre-patterned substrate is beneficial.
Thus, the invention is directed to a process wherein a mask is applied to a pre-patterned substrate, through selective chemical reactions described below, that replicates the underlining pattern. This mask can then be utilized for treatment or material deposition onto specific components of the pre-patterned substrate. The use of the self-aligned masks allows a unique process in which masks can be generated without the need to perform additional pattern defining steps.
Another application of this invention is its use for semiconductor packaging substrates which are comprised of conductors (usually copper) and insulators (usually epoxy, polyimide, alumina, cordierite glass ceramic and the like) disposed adjacent to each other. Commonly, the conductors must be protected from external ambients and processing exposures such as soldering and wet etching. This protection can be achieved by using the various methods of forming selective coatings on the conductor. Alternately, selective coating on the dielectric by one of the exemplary methods can leave the metal exposed for further processing by methods such as electroless plating to add additional metal layers such as nickel, cobalt, palladium, gold and others on top, without exposing the dielectrics to these process steps. The ability to accomplish these selective modifications without the use of lithographic processing leads to cost reductions and is particularly advantageous in microelectronic packaging, which is very cost sensitive.
Although the utilization of the self-aligned masks is described for microelectronic parts, this method is useful for any application whereby the modification of a specific component in a pre-patterned substrate is beneficial.
Thus, this invention is directed to a method for forming a self aligned pattern on an existing pattern on a substrate comprising applying a coating of the masking material to the substrate; and allowing at least a portion of the masking material to preferentially attach to portions of the existing pattern. The pattern may be comprised of a first set of regions of the substrate having a first atomic composition and a second set of regions of the substrate having a second atomic composition different from the first composition. The first set of regions may include one or more metal elements and the second set of regions may include a dielectric. The first regions may comprise copper and may be patterned electrical interconnects.
According to the present invention, the masking material may comprise a polymer containing a reactive grafting site that selectively binds to the portions of the pattern. The polymer may be that of an amorphous polymeric system having chain architecture (including linear, networked, branched and dendrimeric) and may contain one or more monomeric units. The polymer may be selected from the group consisting of polystyrenes, polymethacrylates, polyacrylates, and polyesters, as well as others mentioned below. The polymer may have a reactive functional group serving as the grafting site, the functional group being selected from the group consisting of: acyl chlorides, anhydrides, hydroxys, esters, ethers, aldehydes, ketones, carbonates, acids, epoxies, aziridines, phenols, amines, amides, imides, isocyanates, thiols, sulfones, halides, phosphines, phosphine oxides, nitros, azos, benzophenones, acetals, ketals, diketones, and organosilanes (SixLyRz,) where L is selected from the group consisting of hydroxy, methoxy, ethoxy, acetoxy, alkoxy, carboxy, amines, halogens, R is selected from the group consisting of hydrido, methyl, ethyl, vinyl, phenyl (any alkyl or aryl).
The method may further comprise preparing a polymer to act as the masking material, forming a condensed phase containing the polymer, and contacting the portions of the pattern with the condensed phase. The condensed phase may be a liquid. The liquid may be a solvent for the polymer.
In accordance with another aspect of the invention , the masking material may include a reactive molecule that binds to the portions of the pattern to provide a layer of functional groups suitable for polymerization initiation. The layer may be a molecular monolayer. The reactive molecule may include a first moiety that binds to the portions of the pattern and a second moiety that serves as a polymerization initiator. The first moiety that binds to the portions of the pattern may be selected from the group consisting of acyl chlorides, anhydrides, hydroxys, esters, ethers, aldehydes, ketones, carbonates, acids, epoxies, aziridines, phenols, amines, amides, imides, isocyanates, thiols, sulfones, halides, phosphines, phosphine oxides, nitros, azos, benzophenones, acetals, ketals, diketones, and organosilanes (SixLyRz,) where L is selected from the group consisting of hydroxy, methoxy, ethoxy, acetoxy, alkoxy, carboxy, amines, halogens, R is selected from the group consisting of hydrido, methyl, ethyl, vinyl, phenyl (any alkyl or aryl). The second moiety that serves as a polymerization initiator may be selected from the group consisting of peroxides, nitroxides, halides, azos, peresters, thioesters, hydroxy; metal organics having the stoichiometry of RX where R may consist of: benzyl, cumyl, butyl, alkyl, napthalene, and X may consist of sodium, lithium, and potassium; protonic acids, lewis acids, carbenium salts, tosylates, triflates, benzophenones, aryldiazonium, diaryliodonium, triarylsulfonium, acetals, ketals, and diketones.
The method may comprise applying a reactive monomer to the layer of functional groups, so that the reactive monomer polymerizes on the layer to form a self-aligned mask layer. The polymerization may comprise a chain growth mechanism wherein polymerization proceeds through addition of a monomer to a reactive polymer. The reactive monomer may be any molecule that polymerizes by a chain growth process and may be a substituted ethylenic organic molecule, one of a monomeric ring, a mixture of similar or dissimilar molecules that react with each other to form a covalent bond, and may be oligomeric or polymeric. The reactive monomer may be one that polymerizes when exposed to one of a free radical, an anion, transition metal catalyst, or a cation. The reactive monomer may also be one that polymerizes when exposed to thermal annealing or irradiation. The reactive monomer may be selected from the group consisting of: dienes, alkenes, acrylics, methacrylics, acrylamides, methacrylamides, vinylethers, vinyl alcohols, ketones, acetals, vinylesters, vinylhalides, vinylnitriles, styrenes, vinyl pyridines, vinyl pyrrolidones, vinyl imidazoles, vinylheterocyclics, styrene, cyclic lactams, cyclic ethers, cyclic lactones, cycloalkenes, cyclic thioesters, cyclic thioethers, aziridines, phosphozines, siloxanes, oxazolines, oxazines, and thiiranes.
The method may further comprise applying the reactive monomer in a condensed phase, and contacting the portions of the pattern with the condensed phase. The condensed phase may be a liquid. The liquid may be a solvent for the polymer. Alternatively, the method may further comprise applying the reactive monomer in a vapor phase.
In accordance with another aspect of the invention, the masking material may include a reactive molecule having functional groups suitable for polymerization propagation. The reactive molecule may be comprised of a first moiety that will bind the reactive molecule to the portions of the existing pattern, and a second moiety that serves as a monomeric unit. The first moiety may be selected from the group consisting of: acyl chlorides, anhydrides, hydroxys, esters, ethers, aldehydes, ketones, carbonates, acids, epoxies, aziridines, phenols, amines, amides, imides, isocyanates, thiols, sulfones, halides, phosphines, phosphine oxides, nitros, azos, benzophenones, acetals, ketals, diketones, and organosilanes (SixLyRz,) where L is selected from the group consisting of hydroxy, methoxy, ethoxy, acetoxy, alkoxy, carboxy, amines, halogens, R is selected from the group consisting of hydrido, methyl, ethyl, vinyl, phenyl (any alkyl or aryl). The second moiety may be comprised of a monomer, and may be selected from the group consisting of, dienes, alkenes, acrylics, methacrylics, acrylamides, methacrylamides, vinylethers, vinyl alcohols, ketones, acetals, vinylesters, vinylhalides, vinylnitriles, styrenes, vinyl pyridines, vinyl pyrrolidones, vinyl imidazoles, vinylheterocyclics, styrene, cyclic lactams, cyclic ethers, cyclic lactones, cycloalkenes, cyclic thioesters, cyclic thioethers, aziridines, phosphozines, siloxanes, oxazolines, oxazines, and thiiranes,
The reactive monomer polymerizes when exposed to one of a free radical, an anion, a transition metal catalyst, or a cation. The reactive monomer may be one that polymerizes when exposed to thermal annealing or irradiation. The polymerization of the reactive monomer with the second moiety of the reactive molecule, which serves as a monomeric unit, provides a mechanism where polymerization through the surface bound groups occurs to form a self-aligned mask layer. The reactive monomer may be any monomer that polymerizes by a chain growth process and may be selected from the group consisting of dienes, alkenes, acrylics, methacrylics, acrylamides, methacrylamides, vinylethers, vinyl alcohols, ketones, acetals, vinylesters, vinylhalides, vinylnitriles, styrenes, vinyl pyridines, vinyl pyrrolidones, vinyl imidazoles, vinylheterocyclics, styrene, cyclic lactams, cyclic ethers, cyclic lactones, cycloalkenes, cyclic thioesters, cyclic thioethers, aziridines, phosphozines, siloxanes, oxazolines, oxazines, and thiiranes.
The addition of initiator can be utilized for polymerization or the polymerization can be driven thermally. The initiator may be selected from the group consisting of peroxides, nitroxides, halides, azos, peresters, thioesters, hydroxy; metal organics having the stoichiometry of RX where R may consist of: benzyl, cumyl, butyl, alkyl, napthalene, and X may consist of sodium, lithium, and potassium; protonic acids, lewis acids, carbenium salts, tosylates, triflates, benzophenones, aryldiazonium, diaryliodonium, triarylsulfonium, acetals, ketals, and diketones.
The method may further comprise applying the reactive monomer and initiator in a condensed phase, and contacting the portions of the pattern with the condensed phase. The condensed phase may be a liquid. The liquid may be a solvent for the polymer. Alternatively, a vapor phase may be used.
In accordance with another aspect of the invention, the masking material includes a composition wherein polymerization proceeds by a step growth process whereby reactions that combine monomers and polymers having two or more functionalities that react with each other to produce polymers of a larger molecular weight. The masking material comprises a reactive molecule, wherein reaction of the reactive molecule with the portion of the pattern generates a layer having reactive groups, which participate in step growth polymerization. The reactive molecule comprises a first moiety that binds the reactive molecule to the portions of the pattern, and a second moiety that serves as a reaction site. The first moiety that binds to portions of the pattern may be selected from the group consisting of: acyl chlorides, anhydrides, hydroxys, esters, ethers, aldehydes, ketones, carbonates, acids, epoxies, aziridines, phenols, amines, amides, imides, isocyanates, thiols, sulfones, halides, phosphines, phosphine oxides, nitros, azos, benzophenones, acetals, ketals, diketones, and organosilanes (SixLyRz,) where L is selected from the group consisting of hydroxy, methoxy, ethoxy, acetoxy, alkoxy, carboxy, amines, halogens, R is selected from the group consisting of hydrido, methyl, ethyl, vinyl, phenyl (any alkyl or aryl),hydroxy. The second moiety that serves as a reaction site may be selected from the group consisting of: amines, nitriles, alcohols, carboxylic acids, sulfonic acids, isocyanates, acyl chlorides, esters, amides, anhydrides, epoxies, halides, acetoxy, vinyl, and silanols. The method further comprises applying a reactive monomer, having one or more functionalities to the layer a form a self-aligned mask layer. The one or more functionalities react with each other to form a covalent bond. The reactive monomer may be one that polymerizes when exposed to thermal annealing or irradiation.
The reactive monomer may be comprised of at least two functional groups which may be dissimilar and may be a mixture of dissimilar molecules and may be comprised of functional groups consisting of: amines, nitriles, alcohols, carboxylic acids, sulfonic acids, isocyanates, acyl chlorides, esters, amides, anhydrides, epoxies, halides, acetoxy, vinyl, and silanols.
The method may further comprise applying the reactive monomer in a condensed phase, and contacting the portions of the pattern with the condensed phase. The condensed phase may be a liquid. The liquid may be a solvent for the polymer. Alternatively, a vapor phase may be used. In general, a vapor phase is used only when applying the reactive monomer to functional groups, and not when polymer is applied.
The method may further comprise removing the masking material from portions of the pattern to which it does not attach. The removing may be accomplished by at least one of rinsing, ultrasonication, dissolution, thermolysis, irradiation, decomposition and related removal methods known in the art. Application of the masking material to the substrate may be accomplished by any means known in the art for example: spin-coating, dip coating, spray coating, scan coating, and using a doctor blade. Other methods may be used within the invention.
The method may further comprise chemically treating regions of the substrate prior to applying the coating. The chemically treating may be comprised of at least one of plasma treatment, application of an oxidizing solution, annealing in an oxidizing or reducing atmosphere, and application of a material that renders surface portions of the substrate, to which it is applied, hydrophobic. The chemical treatment changes the wetting characteristics of the regions of the substrate. The chemically treating may comprise applying a molecule having reactive grafting sites that can covalently bind to the dielectric surface including: acyl chlorides, anhydrides, hydroxys, esters, ethers, aldehydes, ketones, carbonates, acids, epoxies, aziridines, phenols, amines, amides, imides, isocyanates, thiols, sulfones, halides, phosphines, phosphine oxides, nitros, azos, benzophenones, acetals, ketals, diketones, and organosilanes (SixLyRz,) where L is selected from the group consisting of hydroxy, methoxy, ethoxy, acetoxy, alkoxy, carboxy, amines, halogens, R is selected from the group consisting of hydrido, methyl, ethyl, vinyl, and phenyl (any alkyl or aryl). The method may further comprise chemically treating regions of the substrate prior to the coating with chemicals that have an affinity to metals. The include chemicals, such as copper binding groups having functional groups comprised of hydroxys, esters, ethers, aldehydes, ketones, carbonates, acids, phenols, amines, amides, imides, thioesters, thioethers, ureas, urethanes, nitriles, isocyanates, thiols, sulfones, halides, phosphines, phosphine oxides, phosphonimides, nitros, azos, thioesters, and thioethers. The functional groups can be heterocyclics, such as benzotriazole, pyridines, imidazoles, imides, oxazoles, benzoxazoles, thiazoles, pyrazoles, triazoles, thiophenes, oxadiazoles, thiazines, thiazoles, quionoxalines, benzimidazoles, oxindoles, and indolines.
The invention is also directed to a structure comprising a self aligned pattern on an existing pattern on a substrate, the self aligned pattern including a masking material having an affinity for portions of the existing pattern, so that the masking material preferentially reactively grafts to the portions of the existing pattern. The pattern may be comprised of a first set of regions of the substrate having a first atomic composition and a second set of regions of the substrate having a second atomic composition different from the first composition. The first set of regions may include one or more metal elements and the second set of regions may include a dielectric. The self-aligned pattern is disposed upon the second set of regions or only upon the second set of regions; that is not upon the first set of regions. The structure may comprise at least one conductive feature, formed on the substrate, with the substrate further comprising at least one insulating layer surrounding the conductive feature. The insulating layer may surround the at least one conductive feature at its bottom and lateral surfaces. The structure may further comprise at least one conductive barrier layer disposed at, at least one interface between the insulating layer and the at least one conductive feature. The combination of the at least one conductive feature and the insulating layers, may be repeated to form a multilevel interconnect stack.
The substrate may be one of a silicon wafer containing microelectronic devices, a ceramic chip carrier, an organic chip carrier, a glass substrate, a gallium arsenide substrate, a silicon carbide substrate, or other semiconductor wafer, a circuit board, or a plastic substrate.
The invention is also directed to a composition for selectively coating a pattern on a substrate, the composition comprising a carrier material for application to the substrate, and a polymer in the carrier that reactively grafts to regions of the substrate having first chemical characteristics. The polymer may be amorphous, may having any chain architecture (including linear, networked, branched, dendrimeric), and can contain one or more monomeric units. The polymer may have acyclic main chains (carbon containing backbones) and may include poly(dienes), poly(alkenes), poly(acrylics), poly(methacrylics), poly(acrylamides), poly(methacrylamides), poly(vinylethers), poly(vinyl alcohols), poly(ketones), poly(acetals), poly(vinylesters), poly(vinylhalides), poly(vinylnitriles), poly(styrenes), poly(vinyl pyridines), poly(vinyl pyrrolidones), poly(vinyl imidazoles), and poly(vinylheterocyclics). If the polymer has a carbocyclic main chain, it may be, for example, a poly(phenylene). The polymer may also be a main chain acyclic heteroatom polymer selected from the group of poly(oxides), poly(carbonates), poly(esters), poly(anhydrides), poly(urethanes), poly(sulfonates), poly(siloxanes), poly(sulfides), poly(thioethers), poly(thioesters), poly(sulfones), poly(sufonamides), poly(amides), poly(imines), poly(ureas), poly(phosphazenes), poly(silanes), poly(siloxanes), poly(silazanes), and poly(nitriles). The polymer may have a heterocyclic main chain and may be selected from the group of poly(imides), poly(oxazoles), poly(benzoxazoles), poly(thiazoles), poly(pyrazoles), poly(triazoles), poly(thiophenes), poly(oxadiazoles), poly(thiazines), poly(thiazoles), poly(quionoxalines), poly(benzimidazoles), poly(oxindoles), poly(indolines), poly(pyridines) poly(triazines), poly(piperazines), poly(pyridines), poly(piperdines), poly(pyrrolidines), poly(carboranes), poly(fluoresceins), poly(acetals), and poly(anhydrides).
The polymer in the carrier may have reactive functional groups that covalently bond to regions of the substrate having first chemical characteristics.